Technical Field
The present invention relates to a microphone, and more specifically relates to a non-directional microphone including an opening portion for pressure equalization.
Background Art
Typically, a non-directional microphone has a diaphragm that is driven by a pressure difference between an outer space (outside air) and an inner space (air chamber) of a housing. Therefore, a space at the back of the diaphragm in the housing in the non-directional microphone is a closed space not communicating into the outer space (outside air).
Meanwhile, in actual designing and productizing, elements such as atmospheric pressure change are taken into account. When the atmospheric pressure is changed, the diaphragm is displaced due to the pressure difference between the outside and the air chamber. If this displacement is large, the diaphragm is broken down. To eliminate such a pressure difference between the outside and the air chamber, a microphone having a structure in which a small opening portion is provided in the housing, and the back-side space of the diaphragm and the outer space communicate through the opening portion is known, for example. The microphone having the structure makes inside/outside pressures of the microphone equal by allowing the back-side space of the diaphragm and the outer space to communicate. The structure making the inside/outside pressures of the microphone equal as described above is called pressure equalization (see JP 2009-060391 A), and the opening portion for the pressure equalization is called pressure equalization opening.
However, when the microphone described in JP 2009-060391 A is used in rainy weather, water drops (rain drops and the like) easily enter the inside of the microphone through the pressure equalization opening. The water drops causes corrosion of internal parts and the like, and becomes a cause of breakdown. Further, if winds and the like are applied to the pressure equalization opening portion at the time of use, a wind noise occurs due to pressure change.